Silicone based conformal coatings that are sprayed on electronic boards are commonly used in automotive and military applications. The silicone coating provides good corrosion and mechanical protection but is difficult and unsafe to apply, and is not easily reworkable. For example, parylene conformal coatings are commercially available but require advanced application methods. Parylene conformal coatings are normally applied in a solid state by a vapor deposition polymerization method. Melt-on waxes are used for protection of electronic components, but they are messy and not easily incorporated into manufacturing processes.
Film wraps are commonly used as oxidative and odor barriers for various food products. Further, metallized bags are frequently used as barriers against odor and water vapor to keep foods dry and crisp, such as for example potato chips. However, these types of barriers can not be vacuum formed or melted onto a component. Further, thermoplastic films alone do not have an effective melt viscosity to provide sufficient wetting, and hence, do not protect against ion migration and corrosion.
A combination of silicone and film is described in U.S. Pat. No. 6,333,117. The '117 patent describes forming a cured silicone resin on a releasing film that acts as a carrier for the silicone. After application of the cured silicone layer to a substrate, the film is removed. Hence, the combination of silicone and film does not supply a protective coating that can be easily removed from a substrate and reworked.
A combination of silicone and film for medical applications is described in U.S. Pat. No. 5,759,560. The '560 patent describes a silicone composition that is bonded to the surface of a thermoplastic splinting material. Hence, a silicone layer is formed and cured prior to application and does not provide sufficient surface and corrosion properties